The present invention relates to a magnetically driven axial-flow pump. More specifically, this invention relates to a pump of which the vane is magnetically driven and which is built in a pipe to feed the fluid in it.
The magnetically driven axial-flow pump of the present invention can be used for any purposes in any technical fields as far as it is supposed to impel the fluid in a pipe. The pump can be used as medical blood pumps, industrial fluid pumps, and engines for movement such as marine motors.
The Japanese Unexamined Patent Publication No. 71492/H5 (1993) disclosed a magnetically driven axial-flow pump.
Referring to FIG. 2, the pump of the prior art will be described. A cylindrical rotor 144 is disposed in an expanded part 140a of a pipe 140 so as to be rotatable freely. An impeller 142 is fixed inside the cylindrical rotor 144. The impeller 142 consists of a shell-shaped stator 142a and vanes 142b, the latter fixed radially to the former. The vanes 142b are also fixed to the inner surface of the cylindrical rotor 144. On the other hand, disposed around the expanded part 140a of the pipe 140 are a stator coil 146 for turning the rotor 144 and magnetic bearings 148 for holding the rotor 144 afloat.
The electromagnetic action between the stator coil 146 and the rotor 144 turns the rotor 144 and hence the impeller 142 to impel the fluid in the pipe 140 in the direction of arrow xe2x80x9cFxe2x80x9d.
The axial flow pump of the prior art has the following shortcomings.
(1) The shell-shaped stator 142a and the vanes 142b have to be made separately and then combined to become the impeller 142. Besides, the vanes 142b have also to be fixed to the inner surface of the cylindrical rotor 144. The assembling work of the stator/rotor assembly is very complex. Although the individual parts can be machined with NC lathes, it is almost impossible to mechanize the assembling work.
(2) In case that the pump is to be used as a blood pump, any gaps have to be sealed, however small they may be. Accordingly, the joints between the stator 142a and the vanes 142b and those between the rotor 144 and the vanes 142b have to be coated somehow, which increases the necessary man-hours. Moreover, because one cannot look at the inside of the stator/rotor assembly once it is assembled, it is impossible to inspect visually the coating condition inside it. Thus, the pump is not reliable enough as a blood pump.
(3) The contact area between the shell-shaped stator 142a and the fluid is relatively large. Accordingly, if the pump is used as a blood pump, it is likely to destroy blood tissues and hence not suitable as a blood pump.
In accordance with the above, the object of the present invention is to provide a magnetically driven axial-flow pump which is easy to manufacture and highly suitable as a blood pump.
According to the present invention, there is provided a magnetically driven axial-flow pump comprising (i) an electromagnet unit arranged about the periphery of a pipe, (ii) a cylindrical rotor accommodated in the pipe, (iii) permanent magnets mounted on the periphery of the rotor, and (iv) a spiral vane formed on the inner surface of the rotor. A hollow is formed in the axial center portion of the vane.
The advantages offered by the present invention are as follows. Because the vane has a hollow in its axial center portion, the rotor and the vane can be made as one piece with an NC machine. Besides, because the occurrence of gaps in the otherwise-inevitable joint between the rotor and the vane is precluded, it is unnecessary to coat such a joint to fill such gaps. Thus, it is easy to make the rotor and the vane.
Furthermore, there are no gaps between the rotor and the vane as mentioned above and there is no object in contact with blood in the center portion of the vane. Therefore, various germs do not enter blood, no thrombi are formed, blood tissues are not destroyed, and hence the pump is suitable as a blood pump.